Display Device

1. A display device with a TFT substrate having a display region on which video signal lines are formed, and a terminal portion, wherein the TFT substrate has a first side at which the terminal portion exists, a second side opposite the terminal portion, a third side at a left side of the terminal portion, and a fourth side at a right side of the terminal portion; a first crack detection terminal is provided at the third side of the terminal portion, and a second crack detection terminal is provided at the fourth side of the terminal portion; a crack detection line extends from the first crack detection terminal along the third, second and fourth sides; and a first switching transistor is provided at the second side between the video signal line and the crack detection line for switching between an image display and crack detection, wherein at the second side, the crack detection line makes a turn at a first fold-back portion around a center of the second side to extend to the third side, makes a turn at a second fold-back portion around the third side to extend to the fourth side, makes a turn at a third fold-back portion around the fourth side to extend to a position around the center of the second side, makes a turn at a fourth fold-back portion around the center of the second side to extend to a position around the fourth side, and further extends along the fourth side.

2. The display device according to claim 1 , wherein a gate of the first switching transistor is controlled by a signal applied to a test gate terminal formed on the terminal portion.

3. The display device according to claim 1 , wherein the terminal portion includes a second switching transistor for switching between the image display and a lighting inspection; a source of the second switching transistor includes a red pixel terminal, a green pixel terminal or a blue pixel terminal which are formed on the terminal portion; and a gate of the first switching transistor is connected to any one of the red pixel terminal, the green pixel terminal and the blue pixel terminal.

4. The display device according to claim 1 , wherein the terminal portion includes a second switching transistor for switching between an image display and a lighting inspection; a third switching transistor is provided between the display region and the second switching transistor, and configured to receive an input of a video signal line, and a lead wire is connected from third switching transistor to the second switching transistor; and the number of the lead wires is ⅓ of the number of the video signal lines.

5. A display device with a TFT substrate having a display region on which scanning lines are formed, and a terminal portion, wherein the TFT substrate has a first side at which the terminal portion exists, a second side opposite the terminal portion, a third side at a left side of the terminal portion, and a fourth side at a right side of the terminal portion; a first crack detection terminal is provided at the third side of the terminal portion, and a second crack detection terminal is provided at the fourth side of the terminal portion; a crack detection line extends from the first crack detection terminal along the third, second and fourth sides; a first switching transistor is provided at the second side between the scanning line and the crack detection line for switching between an image display and crack detection; and wherein at the second side, the crack detection line makes a turn at a first fold-back portion around a center of the second side to extend to the third side, makes a turn at a second fold-back portion around the third side to extend to the fourth side, makes a turn at a third fold-back portion around the fourth side to extend to a position around the center of the second side, makes a turn at a fourth fold-back portion around the center of the second side to extend to a position around the fourth side, and further extends along the fourth side.

6. The display device according to claim 5 , wherein a gate of the first switching transistor is controlled by a signal applied to a test gate terminal formed on the terminal portion.

7. The display device according to claim 5 , wherein the terminal portion includes a second switching transistor for switching between the image display and a lighting inspection; a source of the second switching transistor includes a red pixel terminal, a green pixel terminal, or a blue pixel terminal which is formed on the terminal portion; and a gate of the first switching transistor is connected to any one of the red pixel terminal, the green pixel terminal and the blue pixel terminal.